SKYWAY, Wash. -- A Skyway couple that found a package filled with methamphetamine on their doorstep is trying to figure out who sent it to their home.

"I was home, and I heard a knock on the door," the woman who lives at the home told KOMO News.

The contents of the package she and her husband found on their doorstep has left them worried about revealing their identities.

The box, which was addressed to their Skyway home, arrived last Thursday.

Digging through layers of tissue inside revealed a can containing a package that was sealed in bubble wrap.

"As soon as I started pulling out the bubble wrap, it occurred to me that this is … this has to be some sort of drugs," the woman said. "I put it back in the box, and I told my husband, ‘This is up to you now.’"

She immediately stopped and waited for her husband to come home to inspect it further, she said.

"Very shocking," the man said. "I think I kind of already knew. I was just like … almost in disbelief."

The couple called sheriff’s deputies, who confirmed through tests that the package indeed contained about a pound of meth.

The address listed on the box was the couple’s address. But no one recognized the name it was shipped to, including the couple's current paying house guests.

"To know that somebody is probably casing out your house waiting for this package, and then now the package has gone missing ... it was a no-brainer to go to the cops," the man said.

The King County Sheriff’s Office has now launched an investigation to figure out who sent the package, a spokeswoman told KOMO News.

A return address lists Palmdale, California, so deputies plan to work with police there to see if they can track down the sender, she added.

"We don’t have a rash of these," said King County Sheriff's Sgt. Cindi West. "In fact, we couldn’t think of any other instances anytime recently in the last few years where we’ve had anything even close to this."

The couple admitted they do find a little bit of humor in what happened.

But the shocking delivery has shaken their peace of mind.

They now worry about the impact it could have on their children.

"It’s still a real worry that someone is going to come looking for it," the man said. "It’s quite a bit of contraband to just go missing. Someone is probably wondering where it went and they didn’t intercept the package in time."

A local spokeswoman for the Drug Enforcement Administration told KOMO News she hadn't seen something like this before.

Deputies said the couple did exactly what they were supposed to do in the situation. If you ever find something suspicious in a package, don't touch it, Sgt. West said. You should call police and let officers come out to investigate, she added.